The present invention relates to packet-switched communications networks, and more particularly to the estimation of point-to-point traffic between sources and destinations for use in the engineering and planning of a packet-switched communications network.
Many network engineering functions, including routing, congestion control, network dimensioning, and capacity expansion, benefit from the ability to accurately estimate call-level source-to-destination traffic intensity. While the traffic intensity data need not be known instantaneously, network design and planning requires the time averaged value of such data. Based on this value, network design engineers can project future traffic levels and thus calculate capacity requirements. Engineers subsequently augment the network to satisfy a specified grade of service, such as overall blocking probability, when carrying the projected traffic load.
To properly engineer a network, engineers should conduct a performance evaluation of the network periodically with the purpose of monitoring whether the network is meeting its stated performance objectives. It may not be practical, however, to directly measure the level of end-to-end performance sustained on all paths through the network. For example, end-to-end utilization, end-to-end delay, and call-level traffic loads (e.g., point-to-point traffic) cannot be directly measured from a packet-switched network. One quantity that can be measured more easily is traffic load on each link in the network. If the relationship between link traffic and point-to-point traffic can be established, the point-to-point traffic can be estimated using link traffic measurements.
Methods have previously been developed for estimating point-to-point traffic in circuit-switched networks. Some of these methods are described in Girard, A., Routing and Dimensioning in Circuit-Switched Networks, Addison-Wesley Publishing Company, 1990, and Hegde, M. V., Min, P. S. and Rayes, A., xe2x80x9cEstimation of Exogenous Traffic Based on Link Measurements in Circuit-Switched Networks,xe2x80x9d IEEE Transactions on Communications, Vol. 43, No. 8, pp. 2381-2390, August 1995. These methods, however, cannot be applied directly to packet-switched networks because the operation and traffic patterns of circuit-switched networks are fundamentally different from those of packet-switched networks. The problem of estimating traffic in a packet-switched network is more complex.
It is desirable, therefore, to provide a method for estimating call-level source-destination traffic intensity developed specifically for packet-switched communications networks. It is also desirable to provide a method for estimating call-level source-destination traffic intensity in a packet-switched network using quantities that can be directly measured from the network, such as traffic on each link in the network.
Methods and systems in accordance with the present invention satisfy those desires by estimating source-destination traffic in a packet-switched network based on measured link traffic and the assignment of traffic paths on the network to source-destination pairs.
Methods and systems consistent with the present invention estimate source-to-destination traffic in a packet-switched network by obtaining a measurement of traffic arriving on each of the links in the network, obtaining a measurement of traffic overflowing from each of the links in the network, determining a relationship between the measurements of arriving traffic on each link and the source-destination traffic based on the assignment of traffic paths through the network to source-destination pairs, and determining an estimate of source-destination traffic based on that relationship and the measurement of arriving traffic on each link. A method or system in accordance with an embodiment of the present invention determines an estimator that minimizes or maximizes certain criteria, such as a least-squares estimator or a maximum likelihood estimator.